Not Applicable.
Not applicable.
The present invention relates generally to an electroplating apparatus for plating of semiconductor components, and more particularly to an electroplating apparatus, including a segmented anode array comprising a plurality of concentrically arranged anode segments which can be independently operated to facilitate uniform deposition of electroplated metal on an associated workpiece.
Production of semiconductive integrated circuits and other semiconductive devices from semiconductor wafers typically requires formation of multiple metal layers on the wafer to electrically interconnect the various devices of the integrated circuit. Electroplated metals typically include copper, nickel, gold and lead. Electroplating is effected by initial formation of a so-called seed layer on the wafer in the form of a very thin layer of metal, whereby the surface of the wafer is rendered electrically conductive. This electroconductivity permits subsequent formation of a so-called blanket layer of the desired metal by electroplating in a reactor vessel. Subsequent processing, such as chemical, mechanical planarization, removes unwanted portions of the metal blanket layer formed during electroplating, resulting in the desired patterned metal layer in a semiconductor integrated circuit or micro-mechanism being formed. Formation of a patterned metal layer can also be effected by electroplating.
Subsequent to electroplating, the typical semiconductor wafer or other workpiece is subdivided into a number of individual semiconductor components. In order to achieve the desired formation of circuitry within each component, while achieving the desired uniformity of plating from one component to the next, it is desirable to form each metal layer to a thickness which is as uniform as possible across the surface of the workpiece. However, because each workpiece is typically joined at the peripheral portion thereof in the circuit of the electroplating apparatus (with the workpiece typically functioning as the cathode), variations in current density across the surface of the workpiece are inevitable. In the past, efforts to promote uniformity of metal deposition have included flow-controlling devices, such as diffusers and the like, positioned within the electroplating reactor vessel in order to direct and control the flow of electroplating solution against the workpiece.
In a typical electroplating apparatus, an anode of the apparatus (either consumable or non-consumable) is immersed in the electroplating solution within the reactor vessel of the apparatus for creating the desired electrical potential at the surface of the workpiece for effecting metal deposition. Previously employed anodes have typically been generally disk-like in configuration, with electroplating solution directed about the periphery of the anode, and through a perforate diffuser plate positioned generally above, and in spaced relationship to, the anode. The electroplating solution flows through the diffuser plate, and against the associated workpiece held in position above the diffuser. Uniformity of metal deposition is promoted by rotatably driving the workpiece as metal is deposited on its surface.
The present invention is directed to an electroplating apparatus having a segmented anode array, including a plurality of anode segments which can be independently operated at different electrical potentials to promote uniformity of deposition of electroplated metal on a associated workpiece.
An electroplating apparatus embodying the principles of the present invention includes an electroplating reactor vessel which contains a segmented anode array immersed in electroplating solution held by the vessel. The anode array includes differently dimensioned anode segments, preferably comprising concentrically arranged ring-like elements, with the anode segments being independently operable at different electrical potentials. The flow of electroplating solution about the anode segments is controlled in conjunction with independent operation of the segments, with uniformity of electroplated metal deposition on the workpiece thus promoted.
In accordance with the illustrated embodiments, the present electroplating apparatus includes an electroplating reactor including a cup-like reactor vessel for holding electroplating solution. A segmented anode array in accordance with the present invention is positioned in the reactor vessel for immersion in the plating solution. The electroplating apparatus includes an associated rotor assembly which can be positioned generally on top of the electroplating reactor, with the rotor assembly configured to receive and retain an associated workpiece such as a semiconductor wafer. The rotor assembly is operable to position the workpiece in generally confronting relationship with the anode array, with the surface of the workpiece in contact with the electroplating solution for effecting deposition of metal on the workpiece. The reactor vessel defines an axis, with the workpiece being positionable in generally transverse relationship to the axis.
The anode array comprises a plurality of anode segments having differing dimensions, with the array being operable to facilitate uniform deposition of electroplated metal on the workpiece. In accordance with the illustrated embodiment, the segmented anode array is positioned generally at the lower extent of the reactor vessel in generally perpendicular relationship to the axis defined by the vessel. The anode array comprises a plurality of ring-like, circular anode segments arranged in concentric relationship to each other about the axis. Thus, at least one of the anode segments having a relatively greater dimension is positioned further from the axis than another one of the anode segments having a relatively lesser dimension. In the illustrated embodiment, each of the anode segments is configured to have an annular, ring-shape, with each being generally toroidal. It is presently preferred that the anode segments be generally coplanar, although it will be appreciated that the segments can be otherwise arranged.
The anode array includes a mounting base upon which the ring-like anode segments are mounted. The present invention contemplates various arrangements for directing and controlling flow of the associated electroplating solution. In particular, the mounting base can define at least one flow passage for directing flow of electroplating solution through the mounting base. In one form, a central-most one of the anode segments defines an opening aligned with the reactor vessel axis, with the flow passage defined by the mounting base being aligned with the opening in the central anode segment. In another embodiment, flow passages defined by the mounting base are positioned generally between adjacent ones of the anode segments for directing flow of electroplating solution therebetween. In this embodiment, a plurality of flow passages are provided which are arranged in a pattern of concentric circles to direct flow of electroplating solution between adjacent ones of the concentrically arranged anode segments.
In an alternate embodiment, the mounting base includes a plurality of depending, flow-modulating projections, defining flow channels therebetween, with the projections arranged generally about the periphery of the mounting base. In the preferred form, the present electroplating apparatus includes a control arrangement operatively connected to the segmented anode array for independently operating the plurality of anode segments. This permits the segments to be operated at different electrical potentials, and for differing periods of time, to facilitate uniform deposition of electroplated metal on the associated workpiece. The present invention contemplates that dielectric elements can also be positioned between at least two adjacent ones of the anode segments for further facilitating uniform deposition of electroplated metal on the workpiece.
Other features and advantages of the present invention will become readily apparent from the following detailed description, the accompanying drawings, and the appended claims.